Some interesting points:

  All cryptographic operations involving symmetric or 
  private keys are performed on the client side

  Each general filesystem node (files/folders) has an 
  encrypted attributes object attached to it, which 
  typically contains just the filename.

  All symmetric cryptographic operations are based on 
  AES-128. 

  Each file and each folder node uses its own randomly
  generated 128 bit key. File nodes use the same key 
  for the attribute block and the file data, plus a 
  64 bit random counter start value and a 64 bit meta 
  MAC to verify the file's integrity.

  Each user account uses a symmetric master key to 
  ECB-encrypt all keys of the nodes it keeps in its own
  trees. This master key is stored on MEGA's servers, 
  encrypted with a hash derived from the user's login 
  password.

  In addition to the symmetric key, each user account 
  has a 2048 bit RSA key pair to securely receive data. 
  Its private component is stored encrypted with the 
  user's symmetric master key.

  MEGA supports secure cross-account access to folders.

  MEGA supports secure unauthenticated data delivery. Any 
  fully registered user can receive files or folders in 
  their inbox through their RSA public key.

  (MEGA) is also our first JavaScript project